Error Code P0100

I have got an engine error warning symbol lit up..
I plugged the gizmo in and it proclaimed a code P0100 mass or volume air flow circuit voltage too low..

BUT, My car runs absolutely spot on without the slightest drop off in performance.. In fact I burned off a so called hot hatch from the lights without any problem at all..
It revs all the way to the red zone if I choose to...

I realize it usually means the MAF is on the way out but surely I would notice "limp home mode"??
Or is the fact I have the EGR shunt in position stopping limp home mode ???

I dont want to splash out on a MAF if there is nothing wrong with mine..
What would you suggest ?

Mileage is now 64k